Fighting between primitive tribes consists either of raids on rival settlements (where surprise is important, and disorder inevitable) or of structured and even ritualistic clashes. In either case the struggle is made up of a large number of one-to-one encounters.

This does not fit the pattern or what is normally called a battle. The story of warfare is usually taken as beginning with the first centralized civilizations, capable of placing troops in the field and even of maintaining a standing army. On this basis Mesopotamia and Egypt are the likeliest sites for the first battlefield.

Of the two Mesopotamia is the more prone to warfare. In Egypt a long narrow strip of fertile river valley is virtually secured from invasion by desert to the west and arid highlands to the east. Once a single kingdom has been established, in about 3100 BC, the pharaohs control the region very successfully, without threat from outside, for more than a millennium. In these circumstances the king's soldiers have the role of a police force, with little likelihood of a pitched battle.

By contrast it is difficult to achieve or sustain central control over the more open plains of Mesopotamia. The pattern there is of a constant struggle betweeen city states. Warfare is endemic.

The foot soldiers of Mesopotamia: from 2500 BC

An early glimpse of ranks of soldiers can be seen in the decoration of a musical instrument of about 2500 BC, found in the royal cemetery at Ur. They wear copper helmets (as do the soldiers buried with the ruler) and heavy protective cloaks, and they appear to be armed with battleaxes. Their leaders ride in wagons with solid wheels drawn by four onagers, a local variety of the wild ass.

A Sumerian document implies that a century later the first great Mesopotamian conqueror, Sargon, keeps more than 5000 soldiers as a permanent army. One of the tablets from Ebla, a city further to the north, gives a glimpse of the Brutal military excursions of the time.

Sargon's men march into battle in a solid block, six ranks deep. This formation, known usually by its later Greek name of phalanx, remains for several millennia the basic way of deploying infantry on the battlefield - transforming the men into a more terrifing and effective fighting unit than their individual strengths and skills would amount to in a free-for-all.

The discipline and training of an army is required to hold the phalanx together, if necessary through quite complex movements. The way each phalanx is deployed on the battlefield becomes the main element of a leader's tactics.

Fortification and siege: 8000-2000 BC

The towns which Sargon marches to attack are well fortified - a precaution which has been considered necessary in this part of the world for many centuries. The tower at Jericho dates from not long after 8000 BC. Uruk, a neighbouring city of Ur, provides itself in about 2700 BC with more than 5 miles (8 km) of protective walls.

The tools of siege warfare - ladders to scale the walls, shovels and picks to undermine them - are not invented for this purpose. Only the battering ram (in its basic form a tree trunk with which a large number of men rush against a closed gate) is a specific siege weapon. It is known from about 1900 BC.

No doubt the basic tricks of siege warfare are also known by this time. Miners, attacking the base of a wall, and soldiers, crashing the heavy ram against a gate, are partially protected by temporary roofs above their heads. Archers, with a steady hail of arrows against defenders on the ramparts, prevent rocks being thrown down on those below. Miners support the masonry above them on wooden props; when they leave they set fire to them, hoping to bring the wall down into the cavity.

These are simple devices. Often they prove inadequate. But elaborate siege engines, such as the catapult to fling huge stones, are still many centuries away.

A pharaoh on the warpath: 1469 BC

The first military campaign of which we have a detailed account ends in a battle followed by a siege. It is an expedition undertaken in about 1469 BC by the pharaoh of Egypt, Thutmose III. He later has the details inscribed on the temple walls at Karnak.

The inscription tells how he marches north against a confederation of his enemies. A surprisingly rapid advance, and an approach by an unexpected route, lead to immediate victory in battle. But the enemy take refuge in the walled town of Megiddo, in what is now Israel. It is seven months before they give in. Brief battle and long siege will prove to be a familiar pattern of war (see Battle and siege of Megiddo).

The pharaoh himself travels in a chariot. He also fights from it. Rulers in earlier centuries have been trundled towards the battlefield in heavy wagons with solid wheels, from which they have stepped down to fight on foot. But the two-wheeled chariot is a light enough vehicle to play an important military role.

It is not known how many chariots Thutmose III takes to Megiddo. Two centuries later the balance within an Egyptian army is 50 chariots and 5000 foot soldiers.

From chariot to cavalry: 2nd millennium BC

The light chariot drawn by two horses is a devastating weapon on the battlefields of the second millennium BC - in Mesopotamia, Egypt, Mycenaean Greece and, from about 1200 BC, China. With a highly-trained charioteer controlling the horses, the warrior can dash about the battlefield causing panic and havoc with a thrusting spear or a shower of arrows (from a composite bow). The Aryans, entering India from about 1500 BC, bring with them this irresistible advantage of war chariots.

But the charioteer needs reasonably level ground, and the war chariot will gradually yield pride of place to cavalry. Even so an Assyrian king, as late as the 7th century BC, vividly describes the Carnage of chariot warfare.

The nomadic people of the steppes develop extraordinary skills in horse riding, even though they have the benefit of neither saddle nor stirrups. Riding on only a saddlecloth, with their feet perhaps supported in felt or leather loops, they learn how to shoot while galloping. Their weapon is the composite bow, short enough to fire directly backwards over the horse's rump in the famous Parthian shot.

Their example is followed, albeit in less nimble fashion, by established armies. The kings of Assyria go into battle on horseback from the 9th century BC. The cavalry (still in action at the start of World War I in Europe) has arrived.

The Assyrian war machine: 879-612 BC

Assyria is the first society to make militarism the central policy of state. A regular event each spring is the departure of the army for conquest. At the head of the march are standard bearers and priests; behind them come the king and his bodyguard, followed by the chariots, the cavalry, the infantry and, bringing up the rear, the baggage train.

This great cavalcade moves outwards through territories already under Assyrian control, growing as it moves, for each region is required to contribute troops. Eventually the great army reaches previously unconquered areas.

Resistance may be brief, for the Assyrian custom is to make an example of any town which refuses to capitulate. Siege engines are brought up, and the end is usually swift. Soon citizens of the unfortunate town are dangling on poles all round the city walls. The prophet Ezekiel provides a terrifying imaginary account of a Town besieged, in his vision of Jerusalem destroyed by the wrath of God.

Other towns understand the message and open their gates. If they seem liable to cooperate, they may be incorporated into the Assyrian empire, providing troops for the army in their turn. If not, their people will be taken as slaves and others will be moved into their territory (the probable fate of the lost tribes of Israel after 722 BC).

Any group rash enough to oppose the Assyrians in the field faces formidable opposition. The main fighting force of an Assyrian army is the foot soldiers, wielding slings and spears, or swords and battleaxes of iron, and protected by armour and shields made mainly of leather. But the minority of specialist troops are also highly effective. They work as teams.

Archers on foot, with bows as tall as themselves, are protected by two companions, one carrying a huge shield and the other a spear. The cavalry operate in pairs; one horseman shoots with a composite bow, while his colleague protects him with a shield. Two-wheeled chariots carry a driver and an archer, often with a shield-bearer, or even two.